Long before Luka Magnotta became a household name in Canada and the subject of an international manhunt, he was pursued by a group of online vigilantes desperate to stop a man they were convinced had killed animals for pleasure. (Screen Cap)

Long before Luka Magnotta became a household name in Canada and the subject of an international manhunt, he was pursued by a group of online vigilantes desperate to stop a man they were convinced had killed animals for pleasure.

But for 18 months before his arrest, Magnotta was tracked by an 11-member group of anonymous animal welfare activists who worked under the banner Animal Beta Project. They waded through his innumerable postings, including videos that depicted the killing of kittens. The first, posted online at the end of 2010, showed a young man killing two kittens in a bag with the help of a vacuum. Others involved a python and a bathtub.

All the while, they were stymied by the elusive Magnotta, a man with several aliases who seemed to be everywhere in cyberspace and yet nowhere in real life. Adding to their frustration was the lack of action by authorities in both provinces.

Kelley speaks to group members who went to extreme lengths to identify and locate Magnotta — at one point, they even scoured Google Maps Street View of Montreal to match a specific location they had spotted in a photo he had posted online. (They traced the image to a staircase near McTavish St. and Doctor Penfield Ave. after noticing distinct street lamps in the background, the show reveals).

“No one really cared. We had a lot of trouble getting help, from anybody,” says Ryan Boyle, a former marine who ran the Facebook page, in "the fifth estate" interview.

“All of our information, all of our evidence was gained from the Internet, so to them [officials], it was Internet-based … flim-flam. You know, they didn’t care until he killed a person.”

"Hunting Magnotta" includes exclusive interviews with two people who knew the alleged killer personally. And it suggests at least one Toronto police detective was alarmed enough to warn his colleagues in Montreal that Magnotta's alleged animal abuse could escalate to humans.

"I want to find this guy more than anyone out there," a detective wrote to the group in March in correspondence obtained by "the fifth estate," CBC News reported Friday.

"I still have the email I sent Montreal PD [police department] stating that yes he was only killing cats right now but that the next would be a human."

The program air much of Magnotta's self-shot video and photos, including a chilling clip in which he spurns the advances of an imaginary lover.

It’s compelling viewing that raises a troubling question: Could Magnotta have been stopped sooner?

CBC News Network rebroadcasts "the fifth estate" on Saturdays at 8 p.m. ET and Sundays at 7 p.m. ET. For more information on the fifth estate, visit the website.

Photos from the family of Jun Lin, the victim of Luka Magnotta were given to media Tuesday, April 2, 2013 in Montreal. Preliminary hearing is underway for Luka Rocco Magnotta, the man charged in connection with the infamous body-parts case that made international headlines.

Photos from the family of Jun Lin, the victim of Luka Magnotta were given to media Tuesday, April 2, 2013 in Montreal. Preliminary hearing is underway for Luka Rocco Magnotta, the man charged in connection with the infamous body-parts case that made international headlines.

Photos from the family of Jun Lin, the victim of Luka Magnotta were given to media Tuesday, April 2, 2013 in Montreal. Preliminary hearing is underway for Luka Rocco Magnotta, the man charged in connection with the infamous body-parts case that made international headlines.

Photos from the family of Jun Lin, the victim of Luka Magnotta were given to media Tuesday, April 2, 2013 in Montreal. Preliminary hearing is underway for Luka Rocco Magnotta, the man charged in connection with the infamous body-parts case that made international headlines.

Photos from the family of Jun Lin, the victim of Luka Magnotta were given to media Tuesday, April 2, 2013 in Montreal. Preliminary hearing is underway for Luka Rocco Magnotta, the man charged in connection with the infamous body-parts case that made international headlines.

Photos from the family of Jun Lin, the victim of Luka Magnotta were given to media Tuesday, April 2, 2013 in Montreal. Preliminary hearing is underway for Luka Rocco Magnotta, the man charged in connection with the infamous body-parts case that made international headlines.

Photos from the family of Jun Lin, the victim of Luka Magnotta were given to media Tuesday, April 2, 2013 in Montreal. Preliminary hearing is underway for Luka Rocco Magnotta, the man charged in connection with the infamous body-parts case that made international headlines.

Photos from the family of Jun Lin, the victim of Luka Magnotta were given to media Tuesday, April 2, 2013 in Montreal. Preliminary hearing is underway for Luka Rocco Magnotta, the man charged in connection with the infamous body-parts case that made international headlines.

Photos from the family of Jun Lin, the victim of Luka Magnotta were given to media Tuesday, April 2, 2013 in Montreal. Preliminary hearing is underway for Luka Rocco Magnotta, the man charged in connection with the infamous body-parts case that made international headlines.

Photos from the family of Jun Lin, the victim of Luka Magnotta were given to media Tuesday, April 2, 2013 in Montreal. Preliminary hearing is underway for Luka Rocco Magnotta, the man charged in connection with the infamous body-parts case that made international headlines.

Luka Rocco Magnotta is shown in an artist's sketch in a Montreal court on Wednesday, March 13, 2013. Magnotta has collapsed in court during his preliminary hearing.The notorious suspect in a killing and dismemberment case had been listening to evidence against him, whose contents are subject to a publication ban.

Daran Lin, father of murder victim Jun Lin, leaves the courthouse in Montreal on Tuesday, March 12, 2013. Preliminary hearing is set to start for Luka Rocco Magnotta, the man charged in connection with the infamous body-parts case that made international headlines.

Luka Rocco Magnotta is seen in an artist's sketch in a Montreal court on Monday, March 11, 2013. A preliminary hearing is set to start for Magnotta, the man charged in connection with the infamous body-parts case that made international headlines.Magnotta's lawyers want the public and media barred from attending the hearing, which is to determine if there is enough evidence for a trial.

Daran Lin, father of murder victim Jun Lin, leaves court with his translator Daran Lin in Montreal on Tuesday, March 12, 2013. Preliminary hearing is set to start for Luka Rocco Magnotta, the man charged in connection with the infamous body-parts case that made international headlines.

Alleged killer Luka Rocco Magnotta is seen in court on a artist drawing Wednesday, January 9, 2013 in Montreal. Magnotta is charged with first-degree murder in the slaying and dismemberment of Chinese engineering student Jun Lin.

Luka Rocco Magnotta is taken by police from a Canadian military plane to a waiting van on Monday, June 18, 2012 in Mirabel, Quebec. Magnotta, the lone suspect in a brutal Montreal killing that made headlines around the world, is back home to face justice on Canadian soil. (Montreal Police)

Magnotta lands in Canada (Montreal Police)

Magnotta lands in Canada (Montreal Police)

Mug shot of Luka Rocco Magnotta, released by Montreal Police on Tuesday, June 5, 2012. Magnotta told a judge Tuesday he will not fight his extradition from Germany to Canada, Berlin police say. Magnotta is wanted in Canada on several charges, including first-degree murder, in connection with the killing and dismemberment of Chinese national Jun Lin. (AP Photo/Montreal Police Service via The Canadian Press)

Vancouver Police Deputy Chief Warren Lemcke speaks during a news conference after a human hand was delivered to a school and a human foot to another in Vancouver, B.C., on Tuesday June 5, 2012. Montreal police later confirmed the packages are connected to the dismembered body of a Chinese student found in Montreal last week and the international manhunt for his killer. (THE CANADIAN PRESS/Darryl Dyck)

A man walks his dog past St. George's School where a human foot was delivered to the school earlier in the day in Vancouver, B.C., on Tuesday June 5, 2012. A human hand was also delivered to another Vancouver school Tuesday. (THE CANADIAN PRESS/Darryl Dyck)

A television cameraman films parents and students at False Creek Elementary School after a human hand was delivered to the school earlier in the day in Vancouver, B.C., on Tuesday June 5, 2012. A human foot was also delivered to another Vancouver school Tuesday. (THE CANADIAN PRESS/Darryl Dyck)

A police car leaves the central police detention facility of Berlin supposedly carrying Luka Rocco Magnotta to a Berlin court Tuesday, June 5, 2012. Luka Magnotta, 29, a Canadian porn actor suspected of murdering and dismembering a Chinese was arrested on Monday at an Internet cafe. A cafe employee recognized Magnotta from a newspaper photo and flagged down a police car. (AP Photo/dapd/ Timur Emek)

The internet cafe where Luka Rocco Magnottahe was recognized in the district of Neukoelln in Berlin, Germany, Monday, June 4, 2012. (AP Photo/Markus Schreiber)

This image taken from CCTV obtained by Associated Press video shows Luka Rocco Magnotta entering the Internet cafe in the district of Neukoelln in Berlin, Germany, Monday, June 4, 2012, where Kadir Anlayisli, who works in the cafe recognized him. "I looked at him and thought I knew him from somewhere, because I read newspapers every day," Anlayisli said. (AP Photo/AP Video)

This image taken from CCTV obtained by Associated Press video shows Kadir Anlayisli, a cafe worker waiting for police in the doorway of the Internet cafe in the district of Neukoelln in Berlin, Germany, Monday, June 4, 2012, where Luka Rocco Magnotta was arrested. (AP Photo/AP Video)

In a Wednesday, May 30, 2012 photo, janitor Eric Schoer looks at a blood-stained fridge at an apartment rented by suspect Luka Rocco Magnotta, where police believe a man was murdered and dismembered, in Montreal. (The Canadian Press, Ryan Remiorz)

A police officer removes a package containg a human foot from the Conservative Party headquarters in Ottawa on Tuesday, May 29, 2012. (THE CANADIAN PRESS/Sean Kilpatrick)

The following is a series of photos and self-portraits posted by Magnota on various websites (Facebook)